The first presidential proclamation about Thanksgiving was made by George Washington in 1789. He declared the 26th of November as the date of celebration. In 1863, President Lincoln proclaimed that the last Thursday in November was a national holiday. Finally, in 1941 Congress and President Truman proclaimed the fourth Thursday of November the legal holiday that it is today.

The Research Center will be closed Thursday, November 25, 2009 for Thanksgiving. Normal hours will resume Monday, November 30, 2009.